Inkjet printers print dots by ejecting very small drops of ink onto the print media and typically include a movable carriage that supports one or more print cartridges each having a printhead with a nozzle member having ink ejecting nozzles. The carriage traverses over the surface of the print media. For any line of print, the carriage may make more than one traverse and utilize a varying number of nozzles in the array.
To complete a full line, the print head passes a specified number of times in a single or multi pass pattern. The print mode may have a number of parameters; the number of passes required to fill the area, and the position of the ink droplets at every pass. To define this feature, a matrix is created that defines each position of each pass in which a drop may print. The matrix is called the printmode mask.
Lines, text and graphics are normally printed with all nozzles aligned in the horizontal, or scan, axis. Defects, including, tails, spray drops and spear drops, can result in rough edges, vertical lines, horizontal lines, banding, and changes in hues on the print media. These defects may be due to a number of factors including nozzle alignment, nozzle outs, the firing frequency or the pen or noise.
The pattern on the print media is altered due to nozzle outs. A printhead with small drop volumes but utilizing a larger number of nozzles would increase the probability of a nozzle out, but each would have a decrease in visibility. For an unbiased writing system missing nozzle defects would scale linearly for any given color.
Printheads may develop mechanical noise. These changes to pen alignment through pen to pen alignment or vibration of the printhead may offset the printing pattern in a regular manner leading to a consistent defect such as banding. To offset this effect, the dots may be printed in a micro-stepping process, a multi-pass process, a process using multiple sized dots and inter-placing these dots, or by utilizing a random or Dithering Pattern.
In general, digital printing systems employ a dot placement pattern whereby circular dots are placed on a rectangular co-ordinate system. This pattern is convenient for the calculation of the placement of data. However the circular dots have to be relatively large to completely cover the media with a lot of dot overlap in areas directly between two adjacent dots, and little overlap at the points of the grid that fall between any four neighboring dots. As such, the rectangular system that uses larger drops requires more ink or toner to completely cover the print media. Therefore, what is needed is a printing system that solves the above problems.